Controller and control method for internal combustion engine

ABSTRACT

A controller for an internal combustion engine is configured to execute a regeneration process of burning and removing particulate matter accumulated in an exhaust purification device, a determination process of determining that a deviation between a first change amount and a second change amount is less than or equal to a threshold, the first change amount and the second change amount being change amounts per unit time of the temperature of exhaust gas on the upstream side and the downstream side of the exhaust purification device, respectively, and an anomaly diagnosing process that determines that the exhaust purification device is in a detached state when the determination process determines that the deviation is less than or equal to the threshold. The controller is configured to not execute the determination process during a period from the end of the regeneration process to when a post-regeneration execution condition is met.

BACKGROUND 1. Field

The present disclosure relates to a controller and a control method foran internal combustion engine.

2. Description of Related Art

An exhaust purification device disposed in an exhaust passage has athermal capacity. The heat of the exhaust gas conducted into the exhaustpurification device is consumed by heat exchange with the exhaustpurification device. As a result, there is a difference between a changein an exhaust gas temperature on the upstream side of the exhaustpurification device and a change in the exhaust gas temperature on thedownstream side of the exhaust purification device.

Japanese Laid-Open Patent Publication No. 2020-106028 discloses acontroller for an internal combustion engine that detects that a filterfor trapping particulate matter in exhaust gas has been removed from anexhaust passage. The controller disclosed in the above publicationcompares a change in the exhaust gas temperature on the upstream side ofthe filter with a change in the exhaust gas temperature on thedownstream side of the filter. Then, the controller determines that thefilter has been removed based on a difference between the change in theexhaust gas temperature on the upstream side of the filter and thechange in the exhaust gas temperature on the downstream side of thefilter.

The controller disclosed in the above publication makes an anomalydetermination that an exhaust purification device such as a filter hasbeen removed. Such a controller is required to make an anomalydetermination with high accuracy.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, a controller for an internal combustion engine isprovided. An exhaust purification device is disposed in an exhaustpassage of the internal combustion engine. The controller comprisesprocessing circuitry. The processing circuitry is configured to executea regeneration process, a first change amount calculating process, asecond change amount calculating process, a determination process, andan anomaly diagnosing process. The regeneration process is a process ofburning and removing particulate matter accumulated in the exhaustpurification device. The first change amount calculating process is aprocess of calculating a first change amount that is a change amount perunit time of an upstream-side temperature. The upstream-side temperatureis a temperature of exhaust gas on an upstream side of the exhaustpurification device. The second change amount calculating process is aprocess of calculating a second change amount that is a change amountper unit time of a downstream-side temperature. The downstream-sidetemperature is a temperature of exhaust gas on a downstream side of theexhaust purification device. The determination process is a process ofdetermining that a deviation between the first change amount and thesecond change amount is less than or equal to a threshold. The anomalydiagnosing process is a process of determining that the exhaustpurification device is in a detached state when it is determined in thedetermination process that the deviation is less than or equal to thethreshold. After executing the regeneration process, the processingcircuitry is configured to not execute the determination process duringa period from the end of the regeneration process to when apost-regeneration execution condition is met.

In another general aspect, a control method for an internal combustionengine is provided. An exhaust purification device is disposed in anexhaust passage of the internal combustion engine. The control methodincludes: executing a regeneration process of burning and removingparticulate matter accumulated in the exhaust purification device;calculating a first change amount that is a change amount per unit timeof an upstream-side temperature, the upstream-side temperature being atemperature of exhaust gas on an upstream side of the exhaustpurification device; calculating a second change amount that is a changeamount per unit time of a downstream-side temperature, thedownstream-side temperature being a temperature of exhaust gas on adownstream side of the exhaust purification device; executing adetermination process of determining that a deviation between the firstchange amount and the second change amount is less than or equal to athreshold; determining that the exhaust purification device is in adetached state when it is determined that the deviation is less than orequal to the threshold; and after executing the regeneration process,not executing the determination process during a period from the end ofthe regeneration process to when a post-regeneration execution conditionis met.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of an enginecontrol unit, which is a controller for an internal combustion engineaccording to an embodiment, an engine controlled by the engine controlunit, and a hybrid electric vehicle including the engine.

FIG. 2 is a flowchart showing the procedure of a routine related to aregeneration process executed by the engine control unit of FIG. 1 .

FIG. 3 is a flowchart showing the procedure of a main routine related toan anomaly diagnosing process executed by the engine control unit ofFIG. 1 .

FIG. 4 is a flowchart showing the procedure of a routine related to afuel cutoff requesting process executed by the engine control unit ofFIG. 1 .

FIG. 5 is a flowchart showing the procedure of a routine related to adetermination process of a post-regeneration execution conditionexecuted by the engine control unit of FIG. 1 .

FIG. 6 is a flowchart showing the procedure of a subroutine related tothe anomaly diagnosing process executed by the engine control unit ofFIG. 1 .

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

This description provides a comprehensive understanding of the methods,apparatuses, and/or systems described. Modifications and equivalents ofthe methods, apparatuses, and/or systems described are apparent to oneof ordinary skill in the art. Sequences of operations are exemplary, andmay be changed as apparent to one of ordinary skill in the art, exceptfor operations necessarily occurring in a certain order. Descriptions offunctions and constructions that are well known to one of ordinary skillin the art may be omitted.

Exemplary embodiments may have different forms, and are not limited tothe examples described. However, the examples described are thorough andcomplete, and convey the full scope of the disclosure to one of ordinaryskill in the art.

In this specification, “at least one of A and B” should be understood tomean “only A, only B, or both A and B.”

An engine control unit 110, which is a controller for an internalcombustion engine according to one embodiment, will now be describedwith reference to FIGS. 1 to 6 .

<Configuration of Vehicle>

As shown in FIG. 1 , an engine 10 includes four cylinders #1 to #4. Anintake passage 12 of the engine 10 incorporates a throttle valve 14. Theintake passage 12 includes four intake ports 12 a in a downstreamsection. Each intake port 12 a is provided with a port injection valve16, which injects fuel into the intake port 12 a. Air drawn into theintake passage 12 and fuel injected from the port injection valves 16flow into combustion chambers 20 when intake valves 18 are opened. Theengine 10 is provided with direct injection valves 22, whichrespectively inject fuel into the cylinders #1 to #4. The directinjection valves 22 inject fuel into the combustion chambers 20 in somecases. The air-fuel mixture in each combustion chamber 20 is burned byspark discharge of an ignition plug 24. This generates combustionenergy, which is in turn converted into rotational energy of acrankshaft 26.

The air-fuel mixture burned in the combustion chambers 20 is dischargedto an exhaust passage 30 as exhaust gas when exhaust valves 28 areopened. The exhaust passage 30 is provided with a three-way catalyst 32,which has an oxygen storage capacity, and a gasoline particulate filter(GPF) 34. The three-way catalyst 32 and the GPF 34 are exhaustpurification devices. The GPF 34 includes a filter that trapsparticulate matter (PM) contained in exhaust gas, and supports athree-way catalyst.

A crank rotor 40 having thirty-two teeth 42 is coupled to the crankshaft26. The teeth 42 are generally arranged at 10° C.A intervals on thecrank rotor 40. Thus, the crank rotor 40 also has a toothless section44, at which the interval between the adjacent teeth 42 is wider than10° C.A. The toothless section 44 is designed to indicate a referentialrotation angle of the crankshaft 26.

The crankshaft 26 is mechanically coupled to a carrier C of a planetarygear mechanism 50, which is part of a power splitter. The planetary gearmechanism 50 includes a sun gear S, which is mechanically coupled to arotary shaft 52 a of a first motor-generator 52. The planetary gearmechanism 50 includes a ring gear R, which is mechanically coupled to arotary shaft 54 a of a second motor-generator 54 and to driven wheels60. Alternating-current voltage of an inverter 56 is applied toterminals of the first motor-generator 52. Alternating-current voltageof an inverter 58 is applied to terminals of the second motor-generator54.

<Controller 500>

A controller 500 controls the engine 10, the first motor-generator 52,and the second motor-generator 54. The controller 500 includes theengine control unit 110, which controls the engine 10. The controller500 includes a motor control unit 130, which controls the firstmotor-generator 52 and the second motor-generator 54. The controller 500further includes a general control unit 100, which oversees control ofthe vehicle. The general control unit 100 is connected to the enginecontrol unit 110 and the motor control unit 130. Each of these controlunits includes processing circuitry and a memory storing programsexecuted by the processing circuitry.

The controller 500 controls the engine 10, the first motor-generator 52,and the second motor-generator 54. That is, the controller 500 controlsthe power train of the vehicle. The controller 500 receives detectionsignals from sensors provided at various sections in the vehicle.

The engine control unit 110 operates operated units of the engine 10,such as the throttle valve 14, the port injection valves 16, the directinjection valves 22, and the ignition plugs 24, thereby controllingtorque and the ratios of exhaust components, which are controlledvariables of the engine 10.

The motor control unit 130 operates the inverter 56, thereby controllingthe rotation speed, which is a controlled variable of the firstmotor-generator 52. Further, the motor control unit 130 operates theinverter 58, thereby controlling torque, which is a controlled variableof the second motor-generator 54.

FIG. 1 shows operation signals MS1 to MS6 respectively corresponding tothe throttle valve 14, the port injection valves 16, the directinjection valves 22, the ignition plugs 24, and the inverters 56, 58. Tocontrol controlled variables of the engine 10, the engine control unit110 refers to an intake air amount Ga detected by an air flow meter 80.The engine control unit 110 also refers to an output signal Scr of acrank angle sensor 82, a coolant temperature THW detected by a coolanttemperature sensor 86, and a pressure Pex of exhaust gas flowing intothe GPF 34 detected by an exhaust pressure sensor 88. The motor controlunit 130 refers to an output signal Sm1 from a first rotation anglesensor 90 in order to control the controlled variable of the firstmotor-generator 52. The first rotation angle sensor 90 detects arotation angle of the first motor-generator 52. The motor control unit130 refers to an output signal Sm2 from a second rotation angle sensor92 in order to control the controlled variable of the secondmotor-generator 54. The second rotation angle sensor 92 detects arotation angle of the second motor-generator 54.

Each of the engine control unit 110 and the motor control unit 130 isconnected to the general control unit 100 by a communication line. Thegeneral control unit 100, the motor control unit 130, and the enginecontrol unit 110 exchange and share calculated information andinformation based on detection signals from sensors through CANcommunication.

The general control unit 100 is connected to an accelerator positionsensor 101, a brake sensor 102, and a vehicle speed sensor 103. Theaccelerator position sensor 101 detects an operated amount of theaccelerator. The brake sensor 102 detects an operated amount of thebrake. The vehicle speed sensor 103 detects a vehicle speed, which isthe speed of the vehicle.

An air-fuel ratio sensor 81 is provided in the exhaust passage 30. Theair-fuel ratio sensor 81 is connected to the engine control unit 110.The air-fuel ratio sensor 81 detects an air-fuel ratio.

An upstream-side temperature sensor 87, which detects an upstream-sidetemperature Tin, is connected to the engine control unit 110. Theupstream-side temperature Tin is a temperature of the exhaust gasbetween the three-way catalyst 32 and the GPF 34 in the exhaust passage30. Also, a downstream-side temperature sensor 89, which detects adownstream-side temperature Tout, is connected to the engine controlunit 110. The downstream-side temperature Tout is a temperature of theexhaust gas on the downstream side of the GPF 34.

The engine control unit 110 estimates a catalyst temperature and a GPFtemperature based on an engine load factor KL, an engine rotation speedNE, and the temperatures of the exhaust gas detected by theupstream-side temperature sensor 87 and the downstream-side temperaturesensor 89. The catalyst temperature is the temperature of the three-waycatalyst 32. The GPF temperature is the temperature of the GPF 34.

The engine control unit 110 calculates a counter CNT by counting thenumber of times that the output signal Scr of the crank angle sensor 82has been input. The value of the counter CNT corresponds to the crankangle, and the larger the value, the larger the crank angle. When thecounter CNT reaches 720° C.A, which is a value corresponding to 0° C.A,the counter CNT is reset to 0 again. The crank angle corresponding tothe state in which the counter CNT is 0 is the crank angle at thecompression top dead center.

<Manner in which Fuel Injection is Performed>

The engine control unit 110 changes the manner in which fuel injectionis performed in the engine 10 in accordance with the engine load factorKL and the engine rotation speed NE. For example, in a high-load zone,the engine 10 supplies fuel only by direct injection, which is fuelinjection by the direct injection valves 22. In a low-load zone, theengine 10 supplies fuel only by port injection, which is fuel injectionby the port injection valves 16. The engine 10 may supply fuel by portinjection and direct injection. In this case, the engine control unit110 changes the ratio between the port injection and the directinjection in accordance with the engine load factor KL and the enginerotation speed NE. In this way, the engine 10 forms an air-fuel mixturesuitable for combustion.

The engine rotation speed NE is calculated by the engine control unit110 based on the output signal Scr. The engine load factor KL iscalculated by the engine control unit 110 based on the intake air amountGa and the engine rotation speed NE.

<Regeneration Process>

FIG. 2 shows a procedure in a routine related to a regeneration processexecuted by the engine control unit 110. The routine shown in FIG. 2 isperformed by the processing circuitry repeatedly executing programsstored in the memory at a specific interval. In the followingdescription, the number of each step is represented by the letter Sfollowed by a numeral.

In the routine shown in FIG. 2 , the engine control unit 110 firstacquires the engine rotation speed NE, the engine load factor KL, andthe coolant temperature THW (S10). Next, the engine control unit 110calculates an update amount ΔDPM of an accumulated amount DPM based onthe engine rotation speed NE, the engine load factor KL, and the coolanttemperature THW (S12). The accumulated amount DPM is the amount of PMtrapped by the GPF 34. Specifically, the engine control unit 110calculates the amount of PM in the exhaust gas discharged to the exhaustpassage 30 based on the engine rotation speed NE, the engine load factorKL, and the coolant temperature THW. The engine control unit 110calculates the update amount ΔDPM based on the amount of PM in theexhaust gas and the GPF temperature.

Next, the engine control unit 110 sets a new accumulated amount DPM tothe sum of the accumulated amount DPM and the update amount ΔDPM. Inthis way, the engine control unit 110 updates the accumulated amount DPM(S14). Next, the engine control unit 110 determines whether a flag F is1 (S16). The value 1 of the flag F indicates that a regeneration processfor burning and removing the PM in the GPF 34 is being executed. Thevalue 0 of the flag F indicates that the regeneration process is notbeing executed. When determining that the flag F is 0 (S16: NO), theengine control unit 110 determines whether the accumulated amount DPM isgreater than or equal to a regeneration execution value DPMH (S18). Theregeneration execution value DPMH is a threshold used by the enginecontrol unit 110 to determine that PM needs to be removed based on theaccumulated amount DPM being greater than or equal to the regenerationexecution value DPMH.

When determining that the accumulated amount DPM is greater than orequal to the regeneration execution value DPMH (S18: YES), the enginecontrol unit 110 determines whether an execution condition for theregeneration process is met (S20). The execution condition may be acondition that the logical conjunction of Condition (1) to Condition(3), which are shown below, is true.

Condition (1): a condition that an engine torque command value Te*,which is a command value of torque to the engine 10, is greater than orequal to a specific value Teth. Condition (2): a condition that theengine rotation speed NE is greater than or equal to a specific speed.

Condition (3): a condition that a torque compensation process of S24 canbe executed.

When determining that the logical conjunction is true (S20: YES), theengine control unit 110 executes the regeneration process and assigns 1to the flag F (S22). Specifically, the engine control unit 110 stopsfuel injection from the port injection valve 16 and the direct injectionvalve 22 of the cylinder #1. Then, the engine control unit 110 makes theair-fuel ratio of the air-fuel mixture in the combustion chambers 20 ofthe cylinders #2 to #4 richer than the stoichiometric air-fuel ratio.That is, the regeneration process is a stopping process in which fuelsupply to one of the cylinders is stopped and fuel is supplied to theremaining cylinders. This process discharges oxygen and unburned fuel tothe exhaust passage 30 in order to increase the temperature of the GPF34, thereby burning and removing the PM trapped by the GPF 34. That is,the engine control unit 110 discharges oxygen and unburned fuel to theexhaust passage 30, so as to burn the unburned fuel in the three-waycatalyst 32 and the like, thereby increasing the temperature of theexhaust gas. This raises the temperature of the GPF 34. Also, the enginecontrol unit 110 supplies oxygen to the GPF 34, so as to burn and removePM trapped by the GPF 34.

The cylinder to which supply of fuel is stopped is not limited to thecylinder #1. For example, to prevent an imbalance in the frequency ofstopping fuel supply, the cylinder in which the fuel supply is stoppedmay be switched in a sequential manner.

The engine control unit 110 requests the motor control unit 130 toexecute a process of compensating for the torque fluctuation of thecrankshaft 26 of the engine 10 caused by the stop of the combustioncontrol of the cylinder #1 (S24). Upon receiving the request, the motorcontrol unit 130 superimposes compensation torque on required torque.The required torque is a torque that the second motor-generator 54 isrequired to generate to cause the vehicle to travel. Then, the motorcontrol unit 130 operates the inverter 58 based on the required torqueon which the compensation torque has been superimposed.

Examples of conditions under which the torque compensation process canbe executed may include a condition that the second motor-generator 54has no anomalies and a condition that the battery has enough electricpower to execute the torque compensation process.

When determining that the flag F is 1 (S16: YES), the engine controlunit 110 determines whether the accumulated amount DPM is less than orequal to a stopping threshold DPML (S26). The stopping threshold DPML isa threshold used by the engine control unit 110 to determine that theregeneration process can be stopped based on the accumulated amount DPMbeing less than or equal to the stopping threshold DPML. When theaccumulated amount DPM is less than or equal to the stopping thresholdDPML (S26: YES), the engine control unit 110 stops the regenerationprocess and assigns 0 to the flag F (S28).

When completing the process of S24 or S28, or when making a negativedetermination in the process of S18 or S20, the engine control unit 110temporarily suspends the series of processes shown in FIG. 2 .

<Anomaly Diagnosing Process>

If the exhaust purification device is removed from the exhaust passage30, the exhaust gas cannot be purified. Accordingly, the engine controlunit 110 executes an anomaly diagnosing process in order to determinethat the exhaust purification device is in a detached state.

FIG. 3 shows a procedure in a main routine related to the anomalydiagnosing process executed by the engine control unit 110. The routineshown in FIG. 3 is performed by the processing circuitry executingprograms stored in the memory. During each trip, from when the mainswitch of the vehicle is turned ON to when it is turned OFF, the enginecontrol unit 110 executes the anomaly diagnosing process if the anomalydiagnosing process has not been completed. The engine control unit 110repeatedly executes the anomaly diagnosing process. Specifically, theanomaly diagnosing process is executed once per trip. In the followingdescription, the number of each step is represented by the letter Sfollowed by a numeral.

In the routine shown in FIG. 3 , the engine control unit 110 firstcalculates a temperature change amount (S30). The temperature changeamount includes a change amount of the upstream-side temperature Tin,detected by the upstream-side temperature sensor 87, and a change amountof the downstream-side temperature Tout, detected by the downstream-sidetemperature sensor 89. That is, the engine control unit 110 calculatesthe amount of change in the upstream-side temperature Tin and the amountof change in the downstream-side temperature Tout. The upstream-sidetemperature Tin is the temperature of the exhaust gas flowing into theGPF 34, which is an exhaust purification device. The downstream-sidetemperature Tout is the temperature of the exhaust gas flowing out fromthe GPF 34. Hereinafter, the amount of change in the upstream-sidetemperature Tin is referred to as a first change amount ΔTin. The amountof change in the downstream-side temperature Tout will be referred to asa second change amount ΔTout.

In this manner, the engine control unit 110 executes a first changeamount calculating process of calculating the first change amount ΔTin,which is a change amount per unit time of the upstream-side temperatureTin, which is the temperature of the exhaust gas on the upstream side ofthe exhaust purification device, in the process of S30.

Also, the engine control unit 110 executes a second change amountcalculating process of calculating the second change amount ΔTout, whichis a change amount per unit time of the downstream-side temperatureTout, which is the temperature of the exhaust gas on the downstream sideof the exhaust purification device, in the process of S30.

The engine control unit 110 executes this routine at regular intervals,for example, every 65 milliseconds, and samples the upstream-sidetemperature Tin and the downstream-side temperature Tout. In the firstchange amount calculating process of the S30, the engine control unit110 calculates a difference by subtracting the upstream-side temperatureTin sampled in the previous cycle from the upstream-side temperature Tinsampled in the current cycle. Then, the calculated difference is storedin the memory as the first change amount ΔTin. Similarly, in the secondchange amount calculating process of the S30, the engine control unit110 calculates a difference by subtracting the downstream-sidetemperature Tout sampled in the previous cycle from the downstream-sidetemperature Tout sampled in the current cycle. Then, the calculateddifference is stored in the memory as the second change amount ΔTout.

Next, the engine control unit 110 calculates a moving average value ofthe first change amount ΔTin (S32). To be specific, in the process ofS32, the engine control unit 110 calculates a long-term moving averagevalue of the first change amount ΔTin and a short-term moving averagevalue of the first change amount ΔTin. The long-term moving averagevalue is an exponential moving average, for example, a 10-second movingaverage. The short-term moving average is also an exponential movingaverage, for example, a 3-second moving average.

The exponential moving average is calculated based on the followingExpression (1).

S _(t) =α×Y _(t)+(1−α)×S _(t-1)  Expression (1)

In Expression (1), α represents is a smoothing coefficient. Thesmoothing coefficient α is calculated based on the following Equation(2).

$\begin{matrix}{\alpha = \frac{2}{N + 1}} & {{Expression}(2)}\end{matrix}$

In Expression (2), N represents is the number of samples. When thelong-term moving average value is calculated, the number of times thefirst change amount ΔTin is acquired in 10 seconds is N. When theshort-term moving average value is calculated, the number of times thefirst change amount ΔTin is acquired in 3 seconds is N. Since the firstchange amount ΔTin is calculated every 65 milliseconds, the first changeamount ΔTin is calculated 153 times in 10 seconds. That is, when thelong-term moving average value is calculated, the number of samples is153, so that the smoothing coefficient α is 0.013. Also, the firstchange amount ΔTin is calculated 46 times in 3 seconds. That is, whenthe short-term moving average value is calculated, the number of samplesis 46, so that the smoothing coefficient α is 0.0426.

In Expression (1), S represents an exponential moving average of thefirst change amount ΔTin. In Expression (1), Y represents is the firstchange amount ΔTin. The subscripts t and t−1 indicate a differencebetween calculated times. That is, the subscript t−1 indicates that itis the value calculated in the previous cycle. The initial value of S is0.

As shown in Expression (1), the long-term moving average value and theshort-term moving average value, which are exponential moving averages,are the sum of the product obtained by multiplying the first changeamount ΔTin by the smoothing coefficient α and the product obtained bymultiplying the exponential moving average S calculated in the previouscycle by the difference obtained by subtracting the smoothingcoefficient α from 1.

As described above, when the long-term moving average value iscalculated, the smoothing coefficient α is set to 0.013. When theshort-term moving average value is calculated, the smoothing coefficientα is set to 0.0426.

As described above, in the process of S32, the engine control unit 110executes a first average value calculating process and a second averagevalue calculating process. The first average value calculating processis a process of calculating a short-term moving average value of theupstream-side temperature Tin. The second average value calculatingprocess is a process of calculating a long-term moving average value,which is an exponential moving average in a period longer than a periodin which the short-term moving average value is calculated.

After calculating the long-term moving average value and the short-termmoving average value, the engine control unit 110 calculates a filtertemperature (S34). The engine control unit 110 calculates thetemperature of a portion 10 millimeters away from the front end of theGPF 34 as a front-side temperature TFr. Also, the engine control unit110 calculates the temperature of a portion 10 millimeters away from therear end of the GPF 34 as a rear-side temperature TRr. That is, inprocess of S34, the engine control unit 110 executes a front-endtemperature estimating process of estimating the front-side temperatureTFr and a rear-end temperature estimating process of estimating therear-side temperature TRr. The front-side temperature TFr is thetemperature of a section of the GPF 34 between the center and the frontend, and the rear-side temperature TRr is the temperature of a sectionof the GPF 34 between the center and the rear end.

The front-side temperature TFr is calculated based on the followingExpression (3).

$\begin{matrix}{{TFr}_{t} = {\frac{{Tin} + {{ofs}1} - {TFr}_{t - 1}}{KFr} + {TFr}_{t - 1}}} & {{Expression}(3)}\end{matrix}$

In Expression (3), of s1 represents a front-end offset value. InExpression (3), KFr represents a front-end responsiveness reducingcoefficient. In Expression (3), the subscripts t and t−1 indicate adifference between calculated times. That is, the subscript t−1indicates that it is the value calculated in the previous cycle. Theinitial value of the front-side temperature TFr is the upstream-sidetemperature Tin.

Further, the rear-side temperature TRr is calculated based on thefollowing Expression (4).

$\begin{matrix}{{TRr}_{t} = {\frac{{Tin} + {{ofs}2} - {TRr}_{t - 1}}{KRr} + {TRr}_{t - 1}}} & {{Expression}(4)}\end{matrix}$

In Expression (4), of s2 represents a rear-end offset value. InExpression (4), KRr represents a rear-end responsiveness reducingcoefficient. In Expression (4), the subscripts t and t−1 indicate adifference between calculated times. That is, the subscript t−1indicates that it is the value calculated in the previous cycle. Theinitial value of the rear-side temperature TRr is the upstream-sidetemperature Tin.

The front-end responsiveness reducing coefficient KFr and the rear-endresponsiveness reducing coefficient KRr are determined based on theintake air amount Ga. The front-end responsiveness reducing coefficientKFr and the rear-end responsiveness reducing coefficient KRr decrease asthe intake air amount Ga increases. The rear-end responsiveness reducingcoefficient KRr is smaller than the front-end responsiveness reducingcoefficient KFr.

The magnitude of the front-end offset value of s1 is set such that thetemperature of a section of the GPF 34 that is 10 millimeters from thefront end can be calculated based on Expression (3). The magnitude ofthe rear-end offset value of s2 is set such that the temperature of asection of the GPF 34 that is 10 millimeters from the rear end can becalculated based on Expression (4). That is, the responsiveness reducingcoefficient and the offset value in Expressions (3) and (4) are adjustedby adaptation so that the deviation between results of experiments andsimulations performed in advance and calculation results are minimized.

When calculating the front-side temperature TFr and the rear-sidetemperature TRr through the process of S34, the engine control unit 110determines whether a precondition for executing the anomaly diagnosingprocess is met (S40). The precondition in this case is a condition thatthe logical conjunction of the following conditions (4) and (5) is true.

Condition (4): a condition that no anomaly has occurred in varioussensors connected to the engine control unit 110, that is, all thesensors are normal.

Condition (5): a condition that the anomaly diagnosing process has notbeen completed.

When the precondition is met (S40: YES), the engine control unit 110determines whether the fuel cutoff operation is being executed (S42).The fuel cutoff operation is an operation mode in which the crankshaft26, which is the engine output shaft, is rotated in a state in whichfuel supply is stopped. Since the vehicle is a hybrid electric vehicle,when it is not necessary to operate the engine 10, the crankshaft 26 isnormally stopped immediately after the engine operation is stopped.Thus, in order to perform anomaly diagnosing process in the vehicle, thefirst motor-generator 52 drives the crankshaft 26 so that the crankshaft26 rotates without the supply of fuel in a state in which the engineoperation would normally be stopped. This enables fuel cut-off operationto be achieved.

The flowchart shown in FIG. 4 shows a routine related to an FC requestprocess for switching ON and OFF of an FC request. The FC request is acommand for requesting execution of the fuel cutoff operation. Thisroutine is repeatedly executed by the general control unit 100. As willbe described later, the fuel cutoff operation is executed when the FCrequest is turned ON through this routine.

When this routine is started, the general control unit 100 determineswhether a precondition for operating the FC request is met (S90). Theprecondition in this case is a condition that a logical conjunction ofthe following conditions (6) and (7) is true.

Condition (6): a condition that no anomaly has occurred in varioussensors connected to the controller 500.

Condition (7): a condition that the battery has enough electric power torotate the crankshaft 26 to achieve the fuel cutoff operation.

If the precondition is met (S90: YES), the general control unit 100determines whether the throttle valve 14 is turned OFF (S92). That is,the general control unit 100 determines whether the accelerator isreleased so that the throttle valve 14 is closed.

When determining that the throttle valve 14 is turned OFF (S92: YES),the general control unit 100 turns ON the FC request and resets an FCcounter FCcnt to 0 (S94). When the FC request is turned ON through theprocess of S94, the engine control unit 110 stops fuel supply in theengine 10. At this time, the motor control unit 130 drives thecrankshaft 26 using the first motor-generator 52. The fuel cutoffoperation is thus executed.

Next, the general control unit 100 determines whether the fuel cutoffoperation is being executed (S96). When determining that the throttlevalve 14 has not been turned OFF (S92: NO), the general control unit 100advances the process to S94 without executing the process of S96.

When determining in the process of S96 that the fuel cutoff operation isbeing executed (S96: YES), the general control unit 100 determineswhether determination in the anomaly diagnosing process has beencompleted (S98). The determination in the anomaly diagnosing process isan anomaly determination or a normality determination, which will bediscussed below.

When determining that the determination in the anomaly diagnosis hasalready been completed in the S98 (S98: YES), the general control unit100 turns OFF the FC request (S100). Thus, the fuel cutoff operation isended. When the fuel cutoff operation is ended in this way, the generalcontrol unit 100 ends the series of routines.

When determining that the determination has not been completed in S98(S98: NO), the general control unit 100 increments the FC counter FCcnt(S102). Then, the general control unit 100 determines whether the FCcounter FCcnt is greater than or equal to a threshold FCth (S104).

When determining in S104 that the FC counter FCcnt is less than thethreshold FCth (S104: NO), the general control unit 100 temporarily endsthis routine. In this case, the fuel cutoff operation is continued.

When determining in S104 that the FC counter FCcnt is greater than orequal to the threshold FCth (S104: YES), the general control unit 100turns OFF the FC request (S100). Thus, when the FC counter FCcnt reachesthe threshold FCth before the determination by the anomaly diagnosingprocess is completed, the fuel cutoff operation is ended. When the fuelcutoff operation is ended in this way, the general control unit 100 endsthe series of routines.

If the fuel cutoff operation is continued for an extended period oftime, the temperature of the exhaust purification device becomes low,and the anomaly diagnosing process cannot be executed properly.Therefore, when determining that the FC counter FCcnt is greater than orequal to the threshold FCth (S104: YES), the general control unit 100ends the fuel cutoff operation and interrupts the anomaly diagnosingprocess.

When determining that the precondition is not met in the process of S90(S90: NO), the general control unit 100 ends the series of routineswithout executing the processes of S92 to S104. When determining in theprocess of S96 that the fuel cutoff operation is not being executed(S96: NO), the general control unit 100 ends the series of routineswithout executing the processes of S98 to S104. The fuel cutoffoperation is executed through the FC request process executed by thegeneral control unit 100 as described above.

Referring back to FIG. 3 , when determining in the process of S42 thatthe fuel cutoff operation is being executed (S42: YES), the enginecontrol unit 110 determines whether a determination execution conditionis met (S44). The determination execution condition is a condition thata logical conjunction of the following conditions (8) to (11) is true.

Condition (8): a condition that warm-up has been completed.

Condition (9): a condition that the upstream-side temperature Tinexhibits an increasing tendency and the front-side temperature TFr ishigher than or equal to the rear-side temperature TRr.

Condition (10): a condition that the air-fuel ratio detected by theair-fuel ratio sensor 81 is within a specified range indicating that theengine 10 has been operated at the stoichiometric air-fuel ratio.

Condition (11): a condition that it has been determined that there is noinfluence of the regeneration process.

It is determined that the upstream-side temperature Tin exhibits anincreasing tendency based on a differential value of the short-termmoving average value and a differential value of the long-term movingaverage value, which are calculated through the process of S32, bothbeing greater than or equal to a specified value. The magnitude of thespecified value is set to a magnitude with which it can be determinedthat the upstream-side temperature Tin exhibits an increasing tendencybased on the differential values being greater than or equal to thespecified value. The value of the specified value does not necessarilyneed to be a positive value.

The determination that there is no influence of the regeneration processis performed through a routine shown in FIG. 5 . FIG. 5 is a flowchartshowing the procedure of a determination process of a post-regenerationexecution condition.

This routine is repeatedly executed by the engine control unit 110during operation of the engine 10. As shown in FIG. 5 , when thisroutine is started, the engine control unit 110 determines whether theregeneration process is being executed (S70). In the process of S70,when determining that the regeneration process is being executed (S70:YES), the engine control unit 110 determines that there is an influenceof the regeneration process (S74). Then, the engine control unit 110temporarily ends this routine.

When determining in the process of S70 that the regeneration process isnot being executed (S70: NO), the engine control unit 110 determineswhether the regeneration process was executed in the previous cycle ofthe routine (S72). When determining in the process of S72 that theregeneration process was not executed in the previous cycle (S72: NO),the engine control unit 110 determines that there is no influence of theregeneration process (S86). Then, the engine control unit 110temporarily ends this routine.

In the process of S72, when determining that the regeneration processwas executed in the previous cycle (S72: YES), the engine control unit110 determines whether the intake air amount Ga is greater than or equalto a specified amount Gath (S76). In the process of S76, whendetermining that the intake air amount Ga is greater than or equal tothe specified amount Gath (S76: YES), the engine control unit 110increments a time counter Tcnt (S78). Then, the engine control unit 110determines whether the time counter Tcnt is greater than or equal to athreshold Tth (S80).

In the process of S80, when determining that the time counter Tcnt isgreater than or equal to the threshold Tth (S80: YES), the enginecontrol unit 110 resets the time counter Tcnt to 0 (S82). Then, theengine control unit 110 determines that there is no influence of theregeneration process (S86). Then, the engine control unit 110temporarily ends this routine.

When determining in the process of S80 that the time counter Tcnt isless than the threshold Tth (S80: NO), the engine control unit 110returns to the process of S76. In the process of S76, when determiningthat the intake air amount Ga is less than the specified amount Gath(S76: NO), the engine control unit 110 resets the time counter Tcnt to 0(S84). Then, the engine control unit 110 returns to the process of S76.

In this manner, the engine control unit 110 executes the processes ofS76 to S84 after executing the regeneration process (S72: YES). Then,when the state in which the intake air amount Ga is greater than orequal to the specified amount Gath (S76: YES) continues for a specifiedtime or longer (S80: YES), it is determined that the influence of theregeneration process has disappeared (S86).

The threshold Tth and the specified amount Gath may be set such that itcan be determined that the temperature of the exhaust purificationdevice has dropped to a level that does not adversely affect the anomalydiagnosing process through the processes of S76 to S84.

As described above, the determination execution condition includes acondition that it is determined that there is no influence of theregeneration process. That is, the determination that the influence iseliminated by the process of the S86 is the post-regeneration executioncondition. The post-regeneration execution condition is an executioncondition of the anomaly diagnosing process after the regenerationprocess is executed.

Referring back to FIG. 3 , when determining in the process of S44 thatthe determination execution condition is met (S44: YES), the enginecontrol unit 110 executes the anomaly diagnosing process (S50). When anegative determination is made in the processes of S40 to S44, theengine control unit 110 temporarily ends this routine without executingthe anomaly diagnosing process.

<Anomaly Diagnosing Process>

Next, the contents of the anomaly diagnosing process will be describedwith reference to FIG. 6 . FIG. 6 is a flowchart showing the procedureof a routine related to the anomaly diagnosing process. When the anomalydiagnosing process is started, the engine control unit 110 repeatedlyexecutes this routine.

When this routine is started, the engine control unit 110 determineswhether a stop condition is met (S52). The stop condition is a conditionthat the upstream-side temperature Tin has increased during the anomalydiagnosing process. The anomaly diagnosing process is repeatedlyexecuted during a determination period, which will be discussed below.Therefore, the stop condition is a condition that the upstream-sidetemperature Tin has increased within the determination period. Theengine control unit 110 determines that the upstream-side temperatureTin is increasing based on the fact that the first change amount ΔTincalculated within the determination period is not a negative value.

When determining that the stop condition is not met (S52: NO), theengine control unit 110 determines whether the current time is withinthe determination period (S54). In the process of S54, when determiningthat the current time is within the determination period (S54: YES), theengine control unit 110 calculates a difference Dif (S56). Thedifference Dif is obtained by subtracting the first change amount ΔTinfrom the second change amount ΔTout. Then, the engine control unit 110calculates a cumulative sum ΣDif of the difference Dif. Specifically,the difference Dif calculated through the process of S56 in the currentcycle is added to the cumulative sum ΣDif calculated in the previouscycle. Then, the sum is used as a new cumulative sum ΣDif to update thecumulative sum ΣDif. By starting the calculation of ΣDif through S56 andS58, the engine control unit 110 starts the determination process. Thedetermination period is a period until the upstream-side temperature Tindecreases by a specified temperature, for example, 25° C., from theupstream-side temperature Tin at the time when the determination processis started.

When the cumulative sum ΣDif is calculated through the process of S58,the engine control unit 110 temporarily ends this routine. By repeatedlyexecuting this routine, the difference Dif calculated during thedetermination period is accumulated and the cumulative sum ΣDif isupdated.

As described with reference to FIG. 3 , the anomaly diagnosing processis executed on condition that the fuel cutoff operation is beingexecuted (S42: YES). Therefore, the upstream-side temperature Tingradually decreases while the anomaly diagnosing process is executed.When the upstream-side temperature Tin decreases by the specifiedtemperature, it is determined that the current time is not within thedetermination period in the process of S54 (S54: NO).

Then, the engine control unit 110 calculates a determination parameterXd (S60). The engine control unit 110 divides the cumulative sum ΣDif bythe number of times the difference Dif has been accumulated. The enginecontrol unit 110 employs the quotient thus calculated as thedetermination parameter Xd. That is, the determination parameter Xd isan average value of the difference Dif, which is obtained by subtractingthe first change amount ΔTin from the second change amount ΔTout, in thedetermination period.

Next, the engine control unit 110 determines whether the determinationparameter Xd is greater than a specified value Xth (S62). Whendetermining that the determination parameter Xd is less than or equal tothe specified value Xth in the process of S62 (S62: NO), the enginecontrol unit 110 makes an anomaly determination (S66).

More specifically, in the process of S66, the engine control unit 110determines that the deviation between the first change amount ΔTin andthe second change amount ΔTout during the fuel cutoff operation is lessthan or equal to a threshold based on the determination result in S62.Then, based on this determination result, the engine control unit 110makes an anomaly determination indicating that the GPF 34, which is anexhaust purification device, is in a state of being removed from theexhaust passage 30. When making an anomaly determination, the enginecontrol unit 110 ends this routine. Thus, the anomaly diagnosing processis completed.

When determining that the determination parameter Xd is greater than thespecified value Xth in the process of S62 (S62: YES), the engine controlunit 110 makes a normality determination (S64). That is, the enginecontrol unit 110 determines that the deviation between the first changeamount ΔTin and the second change amount ΔTout during the fuel cutoffoperation is greater than the threshold based on the determinationresult in the S62. Then, based on the determination result, the enginecontrol unit 110 makes a normality determination indicating that the GPF34, which is an exhaust purification device, has not been removed fromthe exhaust passage 30. When making a normality determination, theengine control unit 110 also ends this routine. Thus, the anomalydiagnosing process is completed.

The processes from S54 to S66 in the anomaly diagnosing processcorrespond to a determination process of determining that the deviationbetween the first change amount ΔTin during the fuel cutoff operationand the second change amount ΔTout during the fuel cutoff operation isless than or equal to the threshold.

When determining that the stop condition is met in the process of S52before the anomaly diagnosing process is completed (S52: YES), theengine control unit 110 ends this routine without performing theprocesses of S54 to S66. That is, in this case, the engine control unit110 interrupts the determination process and ends an anomaly process.

Operation of Present Embodiment

When the exhaust purification device is detached, heat exchange is notperformed between the gas conducted into the exhaust purification deviceand the exhaust purification device. Therefore, the deviation betweenthe first change amount ΔTin and the second change amount ΔTout isrelatively small.

When the exhaust purification device is attached, the downstream-sidetemperature Tout changes due to heat exchange between the gas conductedinto the exhaust purification device and the exhaust purificationdevice. Therefore, the deviation between the first change amount ΔTinand the second change amount ΔTout increases.

Therefore, the anomaly determination can be made based on the fact thatthe deviation between the first change amount ΔTin and the second changeamount ΔTout is less than or equal to the threshold.

Further, as the deviation between the temperature of the gas conductedinto the exhaust purification device and the temperature of the exhaustpurification device increases, heat exchange between the gas and theexhaust purification device is more likely to be performed. Therefore,in a state in which the exhaust purification device is attached, thelarger the deviation between the temperature of the gas conducted intothe exhaust purification device and the temperature of the exhaustpurification device, the larger the deviation between the first changeamount ΔTin and the second change amount ΔTout becomes.

During the fuel cutoff operation, air that has passed through thecombustion chamber 20 is conducted into the exhaust purification device.This air has a lower temperature than the exhaust gas. Therefore, thedeviation between the temperature of the air conducted into the exhaustpurification device and the temperature of the exhaust purificationdevice during the fuel cutoff operation is greater than the deviationbetween the exhaust gas and the temperature of the exhaust purificationdevice.

The engine control unit 110 executes the anomaly diagnosing process oncondition that the fuel cutoff operation is being executed (S42: YES).Then, in the determination process, the engine control unit 110determines that the deviation between the first change amount ΔTin whenthe fuel cutoff operation is executed and the second change amount ΔToutwhen the fuel cutoff operation is executed is less than or equal to thethreshold. When it is determined that the deviation is less than orequal to the threshold, the anomaly determination is made (S62: YES,S66).

That is, the engine control unit 110 executes the determination processin a state in which the deviation between the first change amount ΔTinand the second change amount ΔTout differs greatly when comparing thecase in which the exhaust purification device is attached and the casein which the exhaust purification device is detached.

During the fuel-cut operation, air having a temperature lower than thatof the exhaust gas and lower than that of the exhaust purificationdevice is conducted into the exhaust purification device. During thefuel cutoff operation, the temperature of the air conducted into theexhaust purification device, i.e., the upstream-side temperature Tin,gradually decreases. The air conducted into the exhaust purificationdevice during the fuel cutoff operation is warmed by heat exchange withthe exhaust purification device. Accordingly, during the fuel cutoffoperation, the downstream-side temperature Tout decreases more graduallythan the upstream-side temperature Tin. Thus, the second change amountΔTout during the fuel cutoff operation becomes a negative value whoseabsolute value is smaller than that of the first change amount ΔTin.Therefore, if the exhaust purification device is attached, thedetermination parameter Xd, which is the average value of the differenceobtained by subtracting the first change amount ΔTin from the secondchange amount ΔTout in the determination period, becomes a positivevalue.

When the exhaust purification device is detached, heat exchange is notperformed between air and the exhaust purification device. Accordingly,the second change amount ΔTout also becomes a negative value having alarge absolute value. Therefore, the determination parameter Xd becomesa negative value or a positive value smaller than that in the case inwhich the exhaust purification device is attached.

Accordingly, an anomaly diagnosis can be made based on the determinationparameter Xd being less than or equal to the specified value Xth.

However, if the upstream-side temperature Tin increases for some reasonwithin the determination period, the first change amount ΔTin becomes apositive value. In this case, the difference obtained by subtracting thefirst change amount ΔTin from the second change amount ΔTout is a largenegative value. Therefore, the determination parameter Xd becomes small.

Further, when the upstream-side temperature Tin increases, thedetermination period becomes longer. The first change amount ΔTin andthe second change amount ΔTout gradually decrease. Therefore, as thedetermination period becomes longer, the determination parameter Xdbecomes smaller.

In this manner, if the upstream-side temperature Tin increases withinthe determination period, the anomaly determination is likely to be madeeven if the exhaust purification device is attached.

In this regard, when determining that the upstream-side temperature Tinhas increased within the determination period, the engine control unit110 determines that the stop condition has been met (S54: YES) andinterrupts the determination process. As a result, the anomalydiagnosing process is ended without making the anomaly determination.

After the regeneration process is performed, the temperature of theexhaust purification device is high. In addition, the oxidation reactionof the particulate matter may be continuing. If the determinationprocess is executed in such a state, the second change amount ΔToutbecomes unstable, and there is a possibility that an accurate anomalydetermination cannot be made.

After executing the regeneration process, as described with reference toFIG. 5 , the engine control unit 110 does not execute the determinationprocess during the period from the end of the regeneration process towhen the post-regeneration execution condition is met. That is, theengine control unit 110 does not execute the determination process anddoes not make the anomaly determination in the period immediately afterthe end of the regeneration process, during which the determination islikely to be affected by the regeneration process.

Advantages of Present Embodiment

(1) The engine control unit 110 executes the anomaly diagnosing processon condition that the fuel cutoff operation is being executed. Thus, thedetermination process is executed in a state in which the deviationbetween the first change amount ΔTin and the second change amount ΔToutdiffers greatly when comparing the case in which the exhaustpurification device is attached and the case in which the exhaustpurification device is detached. This allows the engine control unit 110make an anomaly determination with higher accuracy.

(2) The determination execution condition includes Condition (9): acondition that the upstream-side temperature Tin exhibits an increasingtendency and the front-side temperature TFr is higher than or equal tothe rear-side temperature TRr. That is, the engine control unit 110starts the determination process on condition that the upstream-sidetemperature Tin exhibits an increasing tendency.

The air conducted into the exhaust purification device during the fuelcutoff operation is warmed by heat exchange with the exhaustpurification device.

When the upstream-side temperature Tin is increasing, the exhaustpurification device is warmed by the exhaust gas conducted into theexhaust purification device from the front end. Therefore, the exhaustpurification device is highly likely to have a temperature gradient inwhich the temperature increases toward the front end and decreasestoward the rear end.

When the exhaust purification device has such a temperature gradient, inwhich the temperature decreases toward the rear end, the air conductedinto the exhaust purification device is less likely to be warmed thanwhen the exhaust purification device has a temperature gradient in whichthe temperature increases toward the rear end or when the exhaustpurification device has no temperature gradient. That is, when theexhaust purification device has a temperature gradient in which thetemperature decreases toward the rear end, the downstream-sidetemperature Tout is lower than when the exhaust purification device hasa temperature gradient in which the temperature increases toward therear end or when the exhaust purification device has no temperaturegradient. Therefore, the second change amount ΔTout is relatively small.On the other hand, during the fuel cutoff operation, the upstream-sidetemperature Tin gradually decreases toward the atmospheric temperature.Therefore, the first change amount ΔTin during the fuel cutoff operationis large.

As described above, when the exhaust purification device is detached,heat exchange between the gas and the exhaust purification device is notperformed. Therefore, the deviation between the first change amount ΔTinand the second change amount ΔTout is relatively small.

That is, the engine control unit 110 starts the determination process ina state in which the deviation between the first change amount ΔTin andthe second change amount ΔTout is likely to increase when the exhaustpurification device is attached. Thus, the engine control unit 110executes the determination process in a state in which the deviationbetween the first change amount ΔTin and the second change amount ΔToutdiffers greatly when comparing the case in which the exhaustpurification device is attached and the case in which the exhaustpurification device is detached. This allows the engine control unit 110make an anomaly determination with higher accuracy.

(3) As described above, the determination execution condition includesCondition (9): a condition that the upstream-side temperature Tinexhibits an increasing tendency and the front-side temperature TFr ishigher than or equal to the rear-side temperature TRr. That is, theengine control unit 110 starts the determination process on conditionthat the front-side temperature TFr is higher than or equal to therear-side temperature TRr.

In this case also, the engine control unit 110 starts the determinationprocess in a state in which the deviation between the first changeamount ΔTin and the second change amount ΔTout is likely to increasewhen the exhaust purification device is attached. This allows the enginecontrol unit 110 make an anomaly determination with high accuracy.

(4) As described above, the determination execution condition includesCondition (10): a condition that the air-fuel ratio detected by theair-fuel ratio sensor 81 is within a specified range indicating that theengine 10 has been operated at the stoichiometric air-fuel ratio. Thatis, the engine control unit 110 starts the determination process oncondition that the air-fuel ratio detected by the air-fuel ratio sensor81 is within a specified range.

If a fuel component is contained in the gas conducted into the exhaustpurification device, the fuel component may cause an oxidation reactionin the exhaust purification device, and the downstream-side temperatureTout may change due to the heat of reaction. If the downstream-sidetemperature Tout fluctuates due to such factors, it is not possible tomake an accurate anomaly determination.

Therefore, the engine control unit 110 does not execute thedetermination process when the air-fuel ratio detected by the air-fuelratio sensor 81 is out of the specified range.

As a result, the engine control unit 110 is prevented from executing thedetermination process when there is a possibility that an accurateanomaly determination cannot be made.

(5) As described above, if the upstream-side temperature Tin increaseswithin the determination period, an anomaly determination is likely tobe made even if the exhaust purification device is attached.

In this regard, when the upstream-side temperature Tin increases withinthe determination period, the engine control unit 110 interrupts thedetermination process. This prevents the engine control unit 110 frommaking an erroneous anomaly determination.

(6) As described above, the determination execution condition includesCondition (11): a condition that it has been determined that there is noinfluence of the regeneration process. That is, after executing theregeneration process, the engine control unit 110 does not execute thedetermination process during the period from the end of the regenerationprocess to when the post-regeneration execution condition is met. Theengine control unit 110 does not execute the determination processduring the period immediately after the end of the regeneration process,in which the determination process is likely to be affected by theregeneration process. Thus, the engine control unit 110 does not make ananomaly determination in a period immediately after the end of theregeneration process. This prevents the engine control unit 110 fromperforming an erroneous anomaly diagnosis.

(7) If the engine operation is continued for a certain amount of timeafter the end of the regeneration process, the temperatures of theexhaust purification device and the exhaust passage 30 converge to atemperature close to the exhaust gas temperature. Further, the oxidationreaction of particulate matter in the exhaust purification device alsosubsides. In this case, the regeneration process no longer affects thedetermination process. Therefore, as described above, the engine controlunit 110 determines that the post-regeneration execution condition ismet when the engine operation in a state in which the intake air amountGa is greater than or equal to the specified amount Gath (S76: YES) hascontinued for a specified period of time or longer (S80: YES) after theend of the regeneration process. This configuration allows the enginecontrol unit 110 to start the determination process when the influenceof the regeneration process no longer affects the determination process.

<Modifications>

The above-described embodiment may be modified as follows. Theabove-described embodiment and the following modifications can becombined if the combined modifications remain technically consistentwith each other.

In the above-described embodiment, the anomaly diagnosing process isexecuted on condition that the fuel cutoff operation is being executed.However, the conditions for the execution of the anomaly diagnosingprocess do not necessarily include the condition that the fuel cutoffoperation is being executed.

In the above-described embodiment, an average value calculated bydividing the cumulative sum ΣDif by the number of times the differenceDif is calculated is used as the determination parameter Xd. However, avalue calculated by another method may be used as the determinationparameter Xd. The determination parameter Xd may be any value serving asan index value indicating the deviation between the first amount ofchange ΔTin and the second amount of change ΔTout. For example, thedetermination parameter Xd may be the cumulative sum ΣDif itself.

Although, in the above-described embodiment, the determination executioncondition includes a condition that the upstream-side temperature Tinexhibits an increasing tendency, the determination execution conditionis not limited to this. For example, the fact that the upstream-sidetemperature Tin exhibits an increasing tendency does not necessarilyneed to be used as the determination execution condition.

The condition for determining that the upstream-side temperature Tinexhibits an increasing tendency is not limited to the use of thelong-term moving average value and the short-term moving average value.For example, only one type of moving average value may be used insteadof two types of moving average values, and it may be determined thatthere is an increasing tendency based on the fact that the differentialvalue of the moving average value is positive.

Although the above-described embodiment compares the front-sidetemperature TFr and the rear-side temperature TRr, and uses the factthat the front-side temperature TFr is higher than the rear-sidetemperature TRr as one of the determination execution conditions, thiscondition may be omitted.

The above-described embodiment uses, as one of the determinationexecution conditions, the logical conjunction of the upstream-sidetemperature Tin exhibiting an increasing tendency and the front-sidetemperature TFr being higher than the rear-side temperature TRr.However, the determination execution conditions may include one of theupstream-side temperature Tin exhibiting an increasing tendency and thefront-side temperature TFr being higher than the rear-side temperatureTRr.

The above-described embodiment includes, as one of the determinationexecution conditions, Condition (10): a condition that the air-fuelratio detected by the air-fuel ratio sensor 81 is within a specifiedrange indicating that the engine 10 has been operated at thestoichiometric air-fuel ratio. The determination execution conditionscan be changed. For example, Condition (10) may be omitted.

Although the determination process is interrupted when the upstream-sidetemperature Tin increases during the determination period, such a stopcondition may be omitted.

The above-described embodiment interrupts the determination process whenit is determined that the upstream-side temperature Tin is increasingbased on the fact that the first change amount ΔTin calculated withinthe determination period is not a negative value. However, the presentdisclosure is not limited thereto. For example, when the first changeamount ΔTin becomes a positive value, it may be determined that theupstream-side temperature Tin is increasing.

The above-described embodiment determines that the post-regenerationexecution condition is met when the engine operation in a state in whichthe intake air amount Ga is greater than or equal to the specifiedamount Gath has continued for the specified period of time or longerafter the end of the regeneration process. However, the presentdisclosure is not limited thereto. For example, it may be determinedthat the post-regeneration execution condition is met when a certainperiod of time has elapsed since the end of the regeneration process.

The specific condition for allowing the regeneration process to beexecuted is not limited to that described in the above-describedembodiment. For example, only one or two of the three conditions (1) to(3) may be used. The specific condition may include a condition otherthan the above-described three conditions. Alternatively, the specificcondition may include none of the three conditions.

A process of estimating the accumulated amount DPM is not limited tothat illustrated in FIG. 2 . The accumulated amount DPM may be estimatedbased on the intake air amount Ga and the pressure difference betweenthe upstream side and the downstream side of the GPF 34. Specifically,the accumulated amount DPM may be estimated to be larger when thepressure difference is relatively large than when the pressuredifference is relatively small. Further, even if the pressure differenceis the same, the accumulated amount DPM may be estimated to be largerwhen the intake air amount Ga is relatively small than when the intakeair amount Ga is relatively large. In a case in which the pressure onthe downstream side of the GPF 34 is regarded to be constant, theabove-described pressure Pex can be used in place of the pressuredifference.

The layout of the three-way catalyst 32 and the GPF 34 in the exhaustpassage 30 may be a layout in which the GPF 34 is disposed on theupstream side of the three-way catalyst 32.

The GPF 34 is not limited to a filter supporting a three-way catalyst,but may be a simple filter. The GPF 34 does not necessarily need to beplaced on the downstream side of the three-way catalyst 32 in theexhaust passage 30. Also, the vehicle does not necessarily need toinclude the GPF 34. For example, even in a case in which the exhaustpurification device includes only the three-way catalyst 32, thestopping process may be executed in order to warm up the three-waycatalyst 32 as described above. The engine control unit 110 may be ofany type if it executes the anomaly diagnosing process in order todetermine whether the exhaust purification device is in a detachedstate.

The vehicle does not necessarily execute the torque compensation processof S24.

The regeneration process of S22, that is, the stopping process, does notnecessarily make the air-fuel ratio in the cylinders other than thestopped cylinder richer. For example, in the case of the regenerationprocess of the GPF 34, when the GPF temperature is sufficiently high sothat the combustion of the particulate matter occurs if oxygen issupplied, it is possible to continue the combustion of particulatematter and advance the regeneration of the GPF 34 without making theair-fuel ratio richer.

The engine control unit 110 is not limited to a device that includesprocessing circuitry and a memory, and executes software processingusing the processing circuitry and the memory. For example, the enginecontrol unit 110 may include a dedicated hardware circuit such as anapplication-specific integrated circuit (ASIC)) that executes at leastpart of the processes executed by the software in the above-describedembodiment. That is, the engine control unit 110 may be processingcircuitry that includes any one of the following configurations (a) to(c).

(a) Processing circuitry including a processor that executes all of theabove-described processes according to programs and a program storagedevice such as a ROM that stores the programs.

(b) Processing circuitry including a processor and a program storagedevice that execute part of the above-described processes according tothe programs and a dedicated hardware circuit that executes theremaining processes.

(c) Processing circuitry including a dedicated hardware circuit thatexecutes all of the above-described processes.

Multiple software processing devices each including a processor and aprogram storage device and multiple dedicated hardware circuits may beprovided.

The vehicle is not limited to a series-parallel hybrid vehicle, but maybe a parallel hybrid vehicle or a series hybrid vehicle. Further, thevehicle is not limited to a hybrid electric vehicle, but may be avehicle that includes only the engine 10 as a drive force generator.

In the above-described embodiment, the engine 10 is an in-linefour-cylinder engine, which includes four cylinders. However, the engine10 controlled by the engine control unit 110 is not limited thereto.That is, the engine 10 is not limited to a four-cylinder engine.Further, the engine 10 may be a V engine, a horizontally opposed engine,or a W engine, in which an exhaust purification device is provided foreach bank. In this case, the stopping process may be configured suchthat fuel supply to at least one cylinder in each of the banks isstopped during one cycle. This permits a sufficient amount of oxygen tobe supplied to the exhaust purification device of each bank of a Vengine or the like.

It should be noted that the expression “at least one” as used hereinmeans “one or more” of the desired options. As an example, theexpression “at least one” as used herein means “only one option” or“both of two options” if the number of options is two. As anotherexample, the expression “at least one” used herein means “only oneoption” or “a combination of any two or more options” if the number ofoptions is three or more.

Various changes in form and details may be made to the examples abovewithout departing from the spirit and scope of the claims and theirequivalents. The examples are for the sake of description only, and notfor purposes of limitation. Descriptions of features in each example areto be considered as being applicable to similar features or aspects inother examples. Suitable results may be achieved if sequences areperformed in a different order, and/or if components in a describedsystem, architecture, device, or circuit are combined differently,and/or replaced or supplemented by other components or theirequivalents. The scope of the disclosure is not defined by the detaileddescription, but by the claims and their equivalents. All variationswithin the scope of the claims and their equivalents are included in thedisclosure.

What is claimed is:
 1. A controller for an internal combustion engine,wherein an exhaust purification device is disposed in an exhaust passageof the internal combustion engine, the controller comprises processingcircuitry, the processing circuitry is configured to execute aregeneration process, a first change amount calculating process, asecond change amount calculating process, a determination process, andan anomaly diagnosing process, the regeneration process is a process ofburning and removing particulate matter accumulated in the exhaustpurification device, the first change amount calculating process is aprocess of calculating a first change amount that is a change amount perunit time of an upstream-side temperature, the upstream-side temperaturebeing a temperature of exhaust gas on an upstream side of the exhaustpurification device, the second change amount calculating process is aprocess of calculating a second change amount that is a change amountper unit time of a downstream-side temperature, the downstream-sidetemperature being a temperature of exhaust gas on a downstream side ofthe exhaust purification device, the determination process is a processof determining that a deviation between the first change amount and thesecond change amount is less than or equal to a threshold, the anomalydiagnosing process is a process of determining that the exhaustpurification device is in a detached state when it is determined in thedetermination process that the deviation is less than or equal to thethreshold, and after executing the regeneration process, the processingcircuitry is configured to not execute the determination process duringa period from the end of the regeneration process to when apost-regeneration execution condition is met.
 2. The controller for theinternal combustion engine according to claim 1, wherein the processingcircuitry is configured to determine that the post-regenerationexecution condition is met when an engine operation in a state in whichan intake air amount is greater than or equal to a specified amount hascontinued for a specified period of time or longer after the end of theregeneration process.
 3. A control method for an internal combustionengine, wherein an exhaust purification device is disposed in an exhaustpassage of the internal combustion engine, and the control methodcomprises: executing a regeneration process of burning and removingparticulate matter accumulated in the exhaust purification device;calculating a first change amount that is a change amount per unit timeof an upstream-side temperature, the upstream-side temperature being atemperature of exhaust gas on an upstream side of the exhaustpurification device; calculating a second change amount that is a changeamount per unit time of a downstream-side temperature, thedownstream-side temperature being a temperature of exhaust gas on adownstream side of the exhaust purification device; executing adetermination process of determining that a deviation between the firstchange amount and the second change amount is less than or equal to athreshold; determining that the exhaust purification device is in adetached state when it is determined that the deviation is less than orequal to the threshold; and after executing the regeneration process,not executing the determination process during a period from the end ofthe regeneration process to when a post-regeneration execution conditionis met.